On 1/25/2011 9:40 PM, p...@mail.nsbeta.info wrote:
I'm reading the document "Secure DNS Deployment Guide" got from the
URL a poster gave in the list.
The document said:
When a user types the URL www.example.com into a Web browser, the
browser program contacts a type of resolver called a stub resolver
that then contacts a local name server (called a recursive name server
or resolving name server). The resolving name server will check its
cache to determine whether it has valid information (the information
is determined to be valid
on the basis of criteria described later in this document) to provide
IP address for the accessed Internet resource
(i.e.,www.marketing.example.com). If not, the resolving name server
checks the cache to determine whether it has the information regarding
the name server for the zone marketing.example.com (since this is the
zone that is expected to contain the resource
www.marketing.example.com). If the name server!ˉs IP address is in the
cache, the resolver!ˉs ne query will be directed against that name
server. If the IP address of the name server of marketing.example.com
is not available in the cache, the resolver determines whether it has
the name server information for a zone that is one level higher than
marketing.example.com (i.e., example.com). If the name server
information for example.com is not available, the next search will be
for the name server of the .com zone in the cache.
I think the statement below is wrong?
If not, the resolving name server checks the cache to determine
whether it > has the information regarding the name server for the
zone marketing.example.com (since this is the zone that is expected
to contain > the resource www.marketing.example.com).
How does the resolver know www.marketing.example.com is a domain name
or a zone? www.marketing.example.com can also be a zone which has
valid NS records. So I was thinking the resolver shall check the cache
firstly to see whether it has the NS records for the zone
www.marketing.example.com, if not, then to check the NS for
marketing.example.com. Am I right?
Yeah, it's wrong. A resolver that followed the algorithm described in
that paper might operate slightly less efficiently than one which
follows the standard resolver algorithm.
But, hey, it's close enough for government work...
- Kevin
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